LTBP1 promotes fibrillin incorporation into the extracellular matrix

Fibrocartilage hyalinization: A potential therapeutic strategy for articular fibrocartilage

Articular fibrocartilage is commonly observed on the joint surface in osteoarthritis (OA) or cartilage injury, often seen as a result of cartilage degeneration. Compared to hyaline cartilage, fibrocartilage exhibits inferior mechanical properties and biological functions, which contribute to further cartilage degeneration and the progression of OA. Despite this, research on cartilage regeneration has not sufficiently addressed the specific challenges and strategies related to fibrocartilage. Although fibrocartilage formation is an unavoidable outcome during cartilage repair, it offers several benefits in the regeneration process, such as providing a natural cell source and establishing a strong integration with surrounding tissues. Recently, a therapeutic approach focused on the in-situ modification of fibrocartilage to promote hyaline cartilage regeneration, referred to as "fibrocartilage hyalinization", has been proposed. Our recent work has demonstrated the feasibility of converting existing fibrocartilage into hyaline cartilage in vivo within the injured area. Key elements of this strategy include modifying the extracellular matrix (ECM), targeting fibrotic chondrocytes, and altering the local microenvironment. This review summarizes the current understanding of articular fibrocartilage's characteristics and mechanisms, while also discussing potential approaches and the feasibility of fibrocartilage hyalinization for cartilage regeneration.

Prenatal diagnosis of geleophysic dysplasia with ADAMTSL2 mutations

OBJECTIVES

We present prenatal diagnosis of Geleophysic dysplasia (GD) at 22 weeks gestation with prenatal ultrasound findings, molecular genetic analysis and postmortem examination.

CASE REPORT

A 27-year-old primigravida was referred at 22 + 4 weeks gestation for detailed anomaly scanning due to routine ultrasound detection of short limbs. Chorionic villus sampling followed by family-based whole-exome sequencing identified two missense ADAMTSL2 variants, both classified as variants of uncertain significance. Detailed ultrasound screening showed short limbs, small hands and feet, typical facial appearance, cardiac and pulmonary anomalies. The association of phenotype and genotype support the diagnosis of GD. Postmortem examination confirmed the prenatal ultrasound findings and the diagnosis of GD.

CONCLUSION

Two missense ADAMTSL2 variants in this case may add new evidence to the molecular diagnosis of GD. Prenatal ultrasound assessment of the fetal phenotype helps us to better interpret fetal genotype, and find the potential causative variants.

Different inflammatory, fibrotic, and immunological signatures between pre-fibrotic and overt primary myelofibrosis

Primary myelofibrosis (PMF) is a myeloid proliferative neoplasm (MPN) characterized by bone marrow fibrosis. Pre-fibrotic PMF (pre-PMF) progresses to overt PMF. Megakaryocytes play a primary role in PMF; however, the functions of megakaryocyte subsets and those of other hematopoietic cells during PMF progression remain unclear. We, therefore, analyzed bone marrow aspirates in cases of pre-PMF, overt PMF, and other MPN using single-cell RNA sequencing. We identified 14 cell types with subsets, including hematopoietic stem and progenitor cells (HSPC) and megakaryocytes. HSPC in overt PMF were megakaryocyte-biased and inflammation/fibrosis-enriched. Among megakaryocytes, the epithelial-mesenchymal transition (EMT)-enriched subset was abruptly increased in overt PMF. Megakaryocytes in non-fibrotic/non-PMF MPN were megakaryocyte differentiation-enriched, whereas those in fibrotic/non-PMF MPN were inflammation/fibrosis-enriched. Overall, the inflammation/fibrosis signatures of the HSPC, megakaryocyte, and CD14+ monocyte subsets increased from pre-PMF to overt PMF. Cytotoxic and dysfunctional scores also increased in T and NK cells. Clinically, megakaryocyte and HSPC subsets with high inflammation/fibrosis signatures were frequent in the patients with peripheral blood blasts ≥1%. Single-cell RNA-sequencing predicted higher cellular communication of megakaryocyte differentiation, inflammation/fibrosis, immunological effector/dysfunction, and tumor-associated signaling in overt PMF than in pre-PMF. However, no decisive subset emerged during PMF progression. Our study demonstrated that HSPC, monocytes, and lymphoid cells contribute to the progression of PMF, and subset specificity existed regarding inflammation/fibrosis and immunological dysfunction. PMF progression may depend on alterations of multiple cell types, and EMT-enriched megakaryocytes may be potential targets for diagnosing and treating the progression.

Mechanisms of assembly and remodelling of the extracellular matrix

The extracellular matrix (ECM) is the complex meshwork of proteins and glycans that forms the scaffold that surrounds and supports cells. It exerts key roles in all aspects of metazoan physiology, from conferring physical and mechanical properties on tissues and organs to modulating cellular processes such as proliferation, differentiation and migration. Understanding the mechanisms that orchestrate the assembly of the ECM scaffold is thus crucial to understand ECM functions in health and disease. This Review discusses novel insights into the compositional diversity of matrisome components and the mechanisms that lead to tissue-specific assemblies and architectures tailored to support specific functions. The Review then highlights recently discovered mechanisms, including post-translational modifications and metabolic pathways such as amino acid availability and the circadian clock, that modulate ECM secretion, assembly and remodelling in homeostasis and human diseases. Last, the Review explores the potential of 'matritherapies', that is, strategies to normalize ECM composition and architecture to achieve a therapeutic benefit.

Insight in the (Phospho)proteome of Vascular Smooth Muscle Cells Derived From Patients With Abdominal Aortic Aneurysm Reveals Novel Disease Mechanisms

BACKGROUND

Abdominal aortic aneurysm (AAA) is characterized by weakening and dilatation of the aortic wall in the abdomen. The aim of this study was to gain insight into cell-specific mechanisms involved in AAA pathophysiology by analyzing the (phospho)proteome of vascular smooth muscle cells derived from patients with AAA compared with those of healthy donors.

METHODS

A (phospho)proteomics analysis based on tandem mass spectrometry was performed on vascular smooth muscle cells derived from patients with AAA (n=24) and healthy, control individuals (C-SMC, n=8). Following protein identification and quantification using MaxQuant, integrative inferred kinase activity analysis was used to calculate kinase activity scores.

RESULTS

Expression differences between vascular smooth muscle cells derived from patients with AAA and healthy, control individuals were predominantly found in proteins involved in ECM (extracellular matrix) remodeling (THSD4 [thrombospondin type-1 domain-containing protein 4] and ADAMTS1 [A disintegrin and metalloproteinase with thrombospondin motifs 1]), energy metabolism (GYS1 [glycogen synthase 1] and PCK2 [phosphoenolpyruvate carboxykinase 2, mitochondrial]), and contractility (CACNA2D1 [calcium voltage-dependent channel subunit α-2/δ-1] and TPM1 [tropomyosin α-1 chain]). Phosphorylation patterns on proteins related to actin cytoskeleton organization dominated the phosphoproteome of vascular smooth muscle cells derived from patients with AAA . Besides, phosphorylation changes on proteins related to energy metabolism (GYS1), contractility (PARVA [α-parvin], PPP1R12A [protein phosphatase 1 regulatory subunit 12A], and CALD1 [caldesmon 1]), and intracellular communication (GJA1 [gap junction α-1 protein]) were seen. Kinase activity of NUAK1 (NUAK family SNF1-like kinase 1), FYN (tyrosine-protein kinase Fyn), MAPK7 (mitogen-activated protein kinase 7), and STK10 (serine/threonine kinase 10) was different in vascular smooth muscle cells derived from patients with AAA compared with those from healthy, control individuals.

CONCLUSIONS

This study revealed changes in expression and phosphorylation levels of proteins involved in various processes responsible for AAA progression and development (eg, energy metabolism, ECM remodeling, actin cytoskeleton organization, contractility, intracellular communication, and cell adhesion). These newly identified proteins, phosphosites, and related kinases provide further insight into the underlying mechanism of vascular smooth muscle cell dysfunction within the aneurysmal wall. Our omics data thereby offer the opportunity to study the relevance, either as drug target or biomarker, of these proteins in AAA development.

Poglut2/3 double knockout in mice results in neonatal lethality with reduced levels of fibrillin in lung tissues

Fibrillin microfibrils play a critical role in the formation of elastic fibers, tissue/organ development, and cardiopulmonary function. These microfibrils not only provide structural support and flexibility to tissues, but they also regulate growth factor signaling through a plethora of microfibril-binding proteins in the extracellular space. Mutations in fibrillins are associated with human diseases affecting cardiovascular, pulmonary, skeletal, and ocular systems. Fibrillins consist of up to 47 epidermal growth factor-like repeats, of which more than half are modified by protein O-glucosyltransferase 2 (POGLUT2) and/or POGLUT3. Loss of these modifications reduces secretion of N-terminal fibrillin constructs overexpressed in vitro. Here, we investigated the role of POGLUT2 and POGLUT3 in vivo using a Poglut2/3 double knockout (DKO) mouse model. Blocking O-glucosylation caused neonatal death with skeletal, pulmonary, and eye defects reminiscent of fibrillin/elastin mutations. Proteomic analyses of DKO dermal fibroblast medium and extracellular matrix provided evidence that fibrillins were more sensitive to loss of O-glucose compared to other POGLUT2/3 substrates. This conclusion was supported by immunofluorescent analyses of late gestation DKO lungs where FBN levels were reduced and microfibrils appeared fragmented in the pulmonary arteries and veins, bronchioles, and developing saccules. Defects in fibrillin microfibrils likely contributed to impaired elastic fiber formation and histological changes observed in DKO lung blood vessels, bronchioles, and saccules. Collectively, these results highlight the importance of POGLUT2/3-mediated O-glucosylation in vivo and open the possibility that O-glucose modifications on fibrillin influence microfibril assembly and or protein interactions in the ECM environment.

Exploring the Regulators of Keratinization: Role of BMP-2 in Oral Mucosa

The oral mucosa functions as a physico-chemical and immune barrier to external stimuli, and an adequate width of the keratinized mucosa around the teeth or implants is crucial to maintaining them in a healthy and stable condition. In this study, for the first time, bulk RNA-seq analysis was performed to explore the gene expression of laser microdissected epithelium and lamina propria from mice, aiming to investigate the differences between keratinized and non-keratinized oral mucosa. Based on the differentially expressed genes (DEGs) and Gene Ontology (GO) Enrichment Analysis, bone morphogenetic protein 2 (BMP-2) was identified to be a potential regulator of oral mucosal keratinization. Monoculture and epithelial-mesenchymal cell co-culture models in the air-liquid interface (ALI) indicated that BMP-2 has direct and positive effects on epithelial keratinization and proliferation. We further performed bulk RNA-seq of the ALI monoculture stimulated with BMP-2 in an attempt to identify the downstream factors promoting epithelial keratinization and proliferation. Analysis of the DEGs identified, among others, IGF2, ID1, LTBP1, LOX, SERPINE1, IL24, and MMP1 as key factors. In summary, these results revealed the involvement of a well-known growth factor responsible for bone development, BMP-2, in the mechanism of oral mucosal keratinization and proliferation, and pointed out the possible downstream genes involved in this mechanism.

Multi-organ phenotypes in mice lacking latent TGFβ binding protein 2 (LTBP2)

BACKGROUND

Latent TGFβ binding protein-2 (LTBP2) is a fibrillin 1 binding component of the microfibril. LTBP2 is the only LTBP protein that does not bind any isoforms of TGFβ, although it may interfere with the function of other LTBPs or interact with other signaling pathways.

RESULTS

Here, we investigate mice lacking Ltbp2 (Ltbp2-/- ) and identify multiple phenotypes that impact bodyweight and fat mass, and affect bone and skin development. The alterations in skin and bone development are particularly noteworthy since the strength of these tissues is differentially affected by loss of Ltbp2. Interestingly, some tissues that express high levels of Ltbp2, such as the aorta and lung, do not have a developmental or homeostatic phenotype.

CONCLUSIONS

Analysis of these mice show that LTBP2 has complex effects on development through direct effects on the extracellular matrix (ECM) or on signaling pathways that are known to regulate the ECM.

Gene Expression Profiling Reveals Potential Players of Sex Determination and Asymmetrical Development in Chicken Embryo Gonads

Despite the notable progress made in recent years, the understanding of the genetic control of gonadal sex differentiation and asymmetrical ovariogenesis in chicken during embryonic development remains incomplete. This study aimed to identify potential key genes and speculate about the mechanisms associated with ovary and testis development via an analysis of the results of PacBio and Illumina transcriptome sequencing of embryonic chicken gonads at the initiation of sexual differentiation (E4.5, E5.5, and E6.5). PacBio sequencing detected 328 and 233 significantly up-regulated transcript isoforms in females and males at E4.5, respectively. Illumina sequencing detected 95, 296 and 445 DEGs at E4.5, E5.5, and E6.5, respectively. Moreover, both sexes showed asymmetrical expression in gonads, and more DEGs were detected on the left side. There were 12 DEGs involved in cell proliferation shared between males and females in the left gonads. GO analysis suggested that coagulation pathways may be involved in the degradation of the right gonad in females and that blood oxygen transport pathways may be involved in preventing the degradation of the right gonad in males. These results provide a comprehensive expression profile of chicken embryo gonads at the initiation of sexual differentiation, which can serve as a theoretical basis for further understanding the mechanism of bird sex determination and its evolutionary process.

The Impact of Mechanical Cues on the Metabolomic and Transcriptomic Profiles of Human Dermal Fibroblasts Cultured in Ultrashort Self-Assembling Peptide 3D Scaffolds

Cells' interactions with their microenvironment influence their morphological features and regulate crucial cellular functions including proliferation, differentiation, metabolism, and gene expression. Most biological data available are based on in vitro two-dimensional (2D) cellular models, which fail to recapitulate the three-dimensional (3D) in vivo systems. This can be attributed to the lack of cell-matrix interaction and the limitless access to nutrients and oxygen, in contrast to in vivo systems. Despite the emergence of a plethora of 3D matrices to address this challenge, there are few reports offering a proper characterization of these matrices or studying how the cell-matrix interaction influences cellular metabolism in correlation with gene expression. In this study, two tetrameric ultrashort self-assembling peptide sequences, FFIK and FIIK, were used to create in vitro 3D models using well-described human dermal fibroblast cells. The peptide sequences are derived from naturally occurring amino acids that are capable of self-assembling into stable hydrogels without UV or chemical cross-linking. Our results showed that 2D cultured fibroblasts exhibited distinct metabolic and transcriptomic profiles compared to 3D cultured cells. The observed changes in the metabolomic and transcriptomic profiles were closely interconnected and influenced several important metabolic pathways including the TCA cycle, glycolysis, MAPK signaling cascades, and hemostasis. Data provided here may lead to clearer insights into the influence of the surrounding microenvironment on human dermal fibroblast metabolic patterns and molecular mechanisms, underscoring the importance of utilizing efficient 3D in vitro models to study such complex mechanisms.

Case report: A homozygous ADAMTSL2 missense variant causes geleophysic dysplasia with high similarity to Weill-Marchesani syndrome

Background: Geleophysic dysplasia and Weill-Marchesani syndrome from the acromelic dysplasias group of genetic skeletal disorders share remarkable clinical and genetic overlap.

Methods: Ophthalmological, physical, radiological examinations were conducted with a female patient in her early 30 s. Whole exome sequencing followed by Sanger sequencing validation was performed to identify the genetic cause.

Results: The patient, born to consanguineous Chinese parents, presented with microspherophakia, lens subluxation, high myopia, short statue, small hands and feet, stiff joints, and thickened skin. A diagnosis of Weill-Marchesani syndrome was initially made for her. However, genetic testing reveals that the patient is homozygous for the c.1966G>A (p.Gly656Ser) variant in ADAMTSL2, and that the patient’s healthy mother and daughter are heterozygous for the variant. As mutations in ADAMTSL2 are known to cause autosomal recessive geleophysic dysplasia, the patient is re-diagnosed with geleophysic dysplasia in terms of her genotype and phenotype.

Conclusion: The present study describes the clinical phenotype of the homozygous ADAMTSL2 p. Gly656Ser variant, which increases our understanding of the genotype-phenotype correlation in acromelic dysplasias.